problem with C# when reading from serial

i have a problem with a serial port reader in C#.

if i send 5555 through the serial port the program prints out 555. here is the program

public static void Main()
{
    byte[] buffer = new byte[256];
    string buff;
    using (SerialPort sp = new SerialPort("COM2", 6200))
    {
        sp.Open();
        //read directly
        sp.Read(buffer, 0, (int)buffer.Length);
        //read using a Stream
        sp.BaseStream.Read(buffer, 0, (int)buffer.Length);
        string开发者_JAVA百科 sir = System.Text.Encoding.Default.GetString(buffer);
        Console.WriteLine(sir);

Both your computer's and the other device's UART may have a hardware buffer which passes data in respect to the actual hardware control enabled for the connection. Hence you have to take care of:

• hardware control flow setup;
• timing of data reading / writing;

Bear in mind you are working with a real-time hardware device that has its own timing which needs to be respected by your application. Communicating with a hardware device is a process. In other words, a one-shot read may not be enough to retrieve all input you are expecting on the logical level.

Update: Google for “SerialPort tutorial C#” and study few of them, like this one.

You need to use the int returned from the "Read" methods. The value returned will tell you how many bytes were actually read. You will probably need to loop and call "Read" multiple times until you have read the number of bytes you need.

Update: This other question has some sample code that shows how to read multiple times until you have enough data to process.